Fiber optic connectors

ABSTRACT

A housing of a fiber optic connector such as an MT-RJ connector has a greater surface area and ridges for improved handling and grasping. A door is provided on a fiber optic connector socket to block light leakage from the socket. The door is compact and does not interfere with neighboring devices while closed. The connector has a housing that centers the ferrule and keeps it in a position for precise alignment with the opposing ferrule. A pin retainer is designed to allow insertion and removal of alignment pins in the field without the need for removing the connector from the fiber optic, so that male connectors can be connected to female connectors and vice-versa.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/473,372, now U.S. Pat. No. 6,464,408, filed Dec. 28, 1999, whichapplication claims the benefit of U.S. Provisional patent applicationSer. No. 60/114,382, filed on Dec. 28, 1998, and also claims the benefitof U.S. Provisional patent application Ser No. 60/134,669, filed on May18, 1999. The disclosures of the aforementioned patent applications areincorporated by reference herein. Said U.S. patent application Ser No.09/473,372, now U.S. Pat. No. 6,464,408, is also related to thecopending, commonly assigned U.S. patent application Ser. No.09/473,370, now abandoned, filed Dec. 28, 1999, the disclosure of whichis hereby incorporated by reference herein.

FIELD OF INVENTION

The present invention relates to the field of fiber optics, and morespecifically relates to improvements in connector components and methodsfor making those improved components.

BACKGROUND OF THE INVENTION

Fiber optic communication systems send messages in the form of pulses oflight along thin strands of transparent material, referred to as fiberoptics. One common application for such systems is in carrying digitaldata between computers in a network or between portions of a largecomputer. In a typical system, a device referred to as an opticaltransmitter includes a laser that emits light. The intensity of thelight is varied in accordance with the information to be sent. Theemitted light is focused on an end of an optical fiber so that the lightis transmitted along the fiber. At the other end of the fiber, the lightis directed onto a photodetector, which transforms the light into anelectrical signal. The electrical signal also varies in accordance withthe information being sent. A “duplex” system typically uses two fibersin parallel, and has a transmitter and a receiver at each end of thesystem so that information can be sent in opposite directions along thetwo fiber optics. The transmitter and receiver at each end typically arecombined in a single device referred to as a “transceiver.” Opticalcommunication systems can transmit data at rates many times faster thansystems using electrical wires, and offer other advantages.

Typically, the optical fibers are provided in optical cables. The fibersthemselves are covered by protective coatings or “sheathing.” The cableincludes one or more individual sheathed fiber optics, covered by anexternal jacket and may also include components for protecting the cableagainst physical strain. To set up an optical communications system,cables of this type are connected to optical devices such astransceivers and to one another in much the same way as electricalcables are connected to electronic devices and to one another to set upan electronic system. However, connecting an optical cable requires thatthe individual optical fibers be precisely aligned with the matingfibers or devices. The optical fibers commonly are as small as 0.125-mm(0.005 inches) in diameter. To connect two fibers end-to-end, the matingends should be aligned with one another within a few microns, i.e.,within hundred-thousandths of an inch, and should be butted against oneanother with essentially no gaps. Even slight deviation from thesetolerances can cause appreciable loss of light transmitted along thefibers and degradation of the signal. Likewise, when an optical cable isconnected to a transceiver or other device, the fibers must be preciselypositioned relative to the optical elements of the device. Opticalcables are provided with devices referred to as “connectors” which canbe engaged with mating connectors on other cables, or with matingfeatures on transceivers or other devices, to align the fibers with therequired precision.

One known type of fiber optic connector is a so-called “MT” type. The MTconnector has a connector housing with a front end and a ferrule movablymounted in the housing. The ferrule is biased by a spring to a forwardposition. When the ferrule is in the forward position, a front face ofthe ferrule projects from the housing. A multi-fiber cable extends intothe housing. The individual fibers of the cable extend through theferrule to the front face. The front face of the ferrule, and the endsof the fibers, are polished to form a flat surface. The fiber ends areprecisely located within the ferrule. The ferrule also has pin-receivingbores. A male MT-type connector has pins in these bores projectingbeyond the front face, whereas a female MT connector has the boresempty. Two cables may be connected to one another by engaging male andfemale MT connectors with one another so that the pins of the maleconnector enter the pin receiving bores of the female connector. Theferrules are free to “float” or move slightly relative to the housing ofthe connectors and hence are brought into precise alignment with oneanother by the pins. Also, because each ferrules is free to moverearwardly relative to its housing against the spring bias, the ferrulescan be brought into abutting, face to face contact despite tolerances inthe housings. These connectors can provide the good connection betweenthe individual fibers of the two cables, with low optical transmissionlosses.

One type of connector that has been proposed is referred to in theindustry as an MT-RJ connector. U.S. Pat. No. 5,926,596 depicts atypical MT-RJ connector. Reference is made to the '596 patent withoutadmission as to whether or not such patent constitutes prior art againstthe present invention. As shown in the '596 patent, a typical MT-RJconnector includes an exterior housing which resembles the exteriorhousing of the common “RJ” plug used to connect a home telephone to awall outlet. The housing has a flexible catch on its exterior. A“ferrule” is movably mounted within the housing at a forward end of thehousing, so that a forward face of the ferrule is exposed to theexterior of the housing. A spring inside the housing urges the ferrulein the forward direction. The ferrule has a pair of fiber bores forreceiving two individual fibers of the cable, and a pair of pin holesfor receiving alignment pins. A “male” MT-RJ connector has alignmentpins permanently disposed in its alignment pin holes, whereas a “female”MT-RJ connector has empty pin holes. The connectors may be permanentlyinstalled on the ends of fiber optic cables by the cable manufacturer.The cable manufacturer positions the fibers in the fiber bores andpolishes the ends of the fiber precisely flush with the front of theferrule.

To connect two cables end-to-end, male and female connectors areinserted into opposite ends of a hollow double-ended socket so that thecatches on their housing engage with the socket and the socketphysically holds the housings in crude alignment with one another. Thepins on the ferrule of the male connector engage the pin holes in theferrule of the female connector, and hold the ferrules, and hence thefibers, in precise alignment with one another. The springs in thehousings urge the ferrules forwardly so that the front faces of theferrules, and hence the ends of the fibers, abut one another. Devicessuch as transceivers are equipped with single-ended sockets adapted toreceive the housing of a connector. Such sockets are equipped with pinscorresponding to the pins of a male MT-RJ connector for engaging theferrule of a female connector so as to hold the ferrule and hence thefibers of the cable in precise alignment with the device.

Despite considerable effort devoted by the art to development of fiberoptic connectors, sockets and related components, there are still needsfor further improvements.

There exists a need for further improvement to the housing of an MT-RJconnector that would allow easier insertion and removal of theconnector. Currently, the housing of MT-RJ connectors are quite smalland do not provide adequate surface area for a technician to grasp theconnector. However, any extension of the surface area of the housing orvariation in shape must conform to industry standards for theseconnectors. A connector that is too large may interfere with neighboringconnectors or sockets by limiting access to those connectors, as in anetwork hub or other computer systems employing fiber optics.

There is also a need to improve the latch mechanism to preventaccidental releases of the connector from the socket.

Regarding the socket, a need exists to provide a socket design thatallows a technician to visually determine, or by touch, the orientationof the socket to ensure that the connector is rotated to the correctposition to have proper alignment of the fiber optics. In a typicalMT-RJ connector, there is only one orientation for both the connectorand the socket that will properly position the fiber optics. As such, akeyway is provided in the socket with an accompanying protrusion on theconnector that matches the keyway. Thus, the connector can only beinserted into the socket in only one way. However, the sockets are quitesmall and are usually positioned inside a computer or in a space that iscrowded with other fiber optic couplers, thus making it difficult for atechnician to find the proper alignment of the connector and socket. Avisual aid on the outside of the socket would allow a technician toidentify the correct orientation of the socket without difficulty.

There also exists a need to improve sockets to prevent the contaminationof the optical interface by dust or other particulate matter enteringthe socket when an end of the socket is open and unoccupied by a cable.Such particulate matter can cause difficulties in making a connection.Also, there exists a need to improve the socket to block light emissionfrom such an unoccupied socket end. If a device is connected to one endof a socket and the other end of the socket is left open, light emittedby the device is sent out into the room environment. The emitted lightcan cause unpleasant sensations if it impinges on the naked eye. Someoccupational and environmental health authorities regard such emittedlight as potentially dangerous. Accordingly, it would be desirable if asocket could be provided with some device to block such emissions whenthe socket is unoccupied. However, any such device should be economicalto manufacture and should not interfere with installation of a connectorin the socket. Moreover, sockets of this type must fit within limitedspace set by industry standards. Any emission-blocking device should notmake the socket appreciably larger, and should allow the socket to meetindustry standards. Taken together, these requirements pose aconsiderable challenge.

A further need persists to improve the ferrule assembly in theconnector. The ferrules of mating connectors must be properly alignedand centered to ensure a proper connection without undue transmissionlosses. Proper alignment also prevents stubbing of the guide pins whenthe connectors are mated. Stubbing occurs when one of the ferrules oftwo mated connectors are off center and the guide pins of the maleconnector are not inserted into the holes of the female connector. Whenstubbing occurs, the ferrules are pushed back into the housing of theconnector, resulting in a misalignment of the fiber optics and thus nolight passing through the coupler.

It would be desirable to provide a connector with the flexibility toallow a field technician to adjust the guide pin placement, depending onfield requirements. In some cases, a transceiver or other connector mayhave a pin placement that does not correspond to the connector to bemated. When this occurs, it would be desirable to adjust the pins of aconnector without having to remove and replace the connector from thefiber optic with a new pin configuration. This would save a tremendousamount of time and labor and reduce the down time of the network system.Such a connector should also be reusable after a pin adjustment.

SUMMARY OF THE INVENTION

The present invention addresses these needs and provides improvementsthat can be used in MT-RJ connectors and in similar connectors. Theimproved connector is described below.

In accordance with one aspect of the invention, a fiber optic connectorcomprises a housing adapted to hold a fiber optic cable. The housing hasa forward direction, upward and downward directions transverse to theforward direction and lateral directions transverse to the forwarddirection and transverse to the upward and downward directions. Thehousing includes a main portion having a downwardly-facing bottomsurface and the housing further includes a forward portion projectingforwardly from the main portion. The connector is used in an assemblywith a generally tubular socket having forward and rearward directions,upward and downward directions transverse to the forward and rearwarddirections of the socket and lateral directions transverse to the otherdirections of the socket. The socket defines a bore extending in theforward and rearward directions. The socket also has a downwardly-facingbottom surface. The bore of the socket is adapted to receive the forwardportion of the housing in a predetermined orientation relative to thesocket so that the directions of the housing are aligned with thecorresponding directions of the socket. A latch for holding the housingand the socket together, and a latch release member disposed above themain portion of the housing are also provided. The latch is adapted torelease the housing from the socket when the latch release member isdepressed toward the main portion of the housing. The bottom surface ofthe main portion projects downward to or below the bottom surface of thesocket when the forward position of the housing is received in the bore.Thus, the bottom surface of the housing main portion is not recessedrelative to the bottom surface of the socket. This allows the technicianto grasp the housing easily.

Preferably, the bottom surface of the socket and the bottom surface ofthe main portion of the housing are generally planar. More preferably,the bottom surfaces of both the socket and the housing main portion aresubstantially coplanar when the forward portion of the housing isreceived in the bore of the socket.

It is also preferred that the bottom surface of the housing main portionhas a pattern of projections and recesses thereon. More preferably,these projections and recesses are in the form of laterally-extendingridges and grooves. The socket and main portion of the housing desirablyeach have laterally-facing, generally planar side surfaces. The sidesurfaces of the housing and socket desirably are substantially coplanarwith one another when the forward portion of the housing is engaged inthe bore. This further facilitates the technician grasping the connectorto insert or remove it from the socket. The housing desirably also hasridges and grooves to aid in grasping. The housing for the connector,however, desirably does not extend past the perimeter of the socket,when viewed front to rear. The increase in surface area does notinterfere with the ability of the technician to handle neighboringconnectors or other devices in proximity to the connector.

The latch release member desirably is resilient and formed integrallywith the main portion of the housing. The latch includes an armprojecting forwardly from the latch release member over the forwardposition of the housing, and a barb projecting upwardly from the armremote from the latch release member. The socket also has a recess forengaging the barb.

According to another aspect of the present invention, a fiber opticconnector assembly comprises a housing adapted to hold a fiber opticcable. The housing has a forward direction, upward and downwarddirections transverse to the forward direction and lateral directionstransverse to the forward direction and transverse to the upward anddownward directions as described above. The housing includes a mainportion and a forward portion projecting forwardly from the main portionalso described above. The housing further includes a resilient latchrelease member projecting upwardly and forwardly from the main portionof the housing and a latch arm formed integrally with the latch releasemember and projecting forwardly from the release member above theforward portion. A barb with a rearwardly-facing catch surface projectsupwardly from the arm at a forward end of the arm remote from the latchrelease member. The fiber optic connector further comprises a sockethaving forward and rearward directions, upward and downward directionstransverse to the forward direction of the socket and lateral directionstransverse to other directions of the socket. The socket defines a rearface and a bore extending forwardly from the rear face. The socket has atop wall with an interior surface facing downwardly towards the bore.The top wall has a pocket open to the interior surface and anaxially-facing catch surface extending to the interior surface. The boreof the socket is adapted to receive the forward portion of the housingand the arm in a predetermined orientation relative to the socket sothat directions of the housing are aligned with the correspondingdirections of the socket and so that the arm faces toward the top walland the barb is received in the pocket with the catch surface of thebarb confronting the catch surface of the top wall. The top wall definesa ramp surface sloping downwardly in the forward direction of thesocket. The ramp surface overlies the arm when the housing is engagedwith the socket and rear portions of the ramp surface remote from theengaged catch surfaces are spaced upwardly from the arm. Spacing of therear portion of the ramp surface from the arm helps to preventinadvertent release of the catch responsive to vertical forces appliedto the connector housing in service. This aspect of the inventionincorporates the realization that inadvertent releases of the latch canbe caused by engagement between the rear portion of the arm and thesocket if the housing is forced upwardly during service. Providing aclearance alleviates this problem.

Preferably, the latch release member includes a beam having a firstportion projecting upwardly and forwardly from the main portion of thehousing and having a second portion projecting downwardly from the mainportion. The beam is preferably flexible at least at the junctionbetween the first and second portions. The beam is desirably formedintegrally with the housing, is less than about 1-mm thick and isunreinforced at least at the junction between the first and secondportions.

According to a further aspect of the present invention, a socket forreceiving a fiber optic connector housing is provided. The socket hasforward and rearward directions, upward and downward directionstransverse to the forward and rearward directions and lateral directionstransverse to the other the directions. The socket defines a boreextending in the forward and rearward directions. The bore has aprincipal portion and a keyway extending along the top of the principalportion. The keyway has lateral dimensions less than the lateraldimensions of the bore. The socket has an exterior profile including aprincipal portion having a first width and a top portion having a secondwidth less than the first width. The top portion and the principalportion cooperatively define a pair of ledges extending axially onopposite sides of the top portion. The principal portion of the bore isdisposed in the principal portion of the exterior shape. The keywayextends in the top portion. This aspect of the current inventionincorporates the realization that technicians had difficulty indetermining the orientation of the keyway of the socket. The ledgesprovide visual and tactile reference, to the top of the keyway, thusindicating the proper orientation for the connector to be inserted intothe socket.

Another aspect of the invention provides a socket for receiving a fiberoptic connector housing. The socket has forward and rearward directions,upward and downward directions transverse to the forward and rearwarddirections and lateral directions transverse to the other saiddirections. The socket defines a bore having an opening at the rearwardend of the housing and extending forwardly into the housing. The housinghas a panel mounting portion spaced forwardly from the rear end of thehousing. A door and one or more hinges supporting the door on thehousing are also provided for pivoting movement about a vertical axisbetween a closed position in which the door blocks the opening of thebore and an open position in which the door does not block the opening.A spring is also disposed outside of the housing. The door, the hingesand the spring have width and height dimensions equal to or smaller thanthe width and height dimensions of the panel mounting portion.

Preferably, the housing defines a first indentation at the rearward endof the housing and the hinges include a top hinge disposed in the firstindentation. The housing defines a bottom surface at the rearward end ofthe housing. The bottom surface desirably is recessed upwardly relativeto the bottom surface of the panel engaging portion, and the hingesinclude a bottom hinge overlying the recessed bottom surface.Preferably, the recessed bottom surface extends laterally across theexterior of the housing and the door defines a bottom overhang whichprojects downwardly beyond the recessed bottom surface. The firstindentation may be disposed on one lateral side of the housing and thehousing desirably defines a second indentation on the opposite lateralside. The door has an overhang portion which is aligned with the secondindentation. As discussed above, the housing may defines a main bore anda keyway having width smaller than said main bore. The keyway may bedisposed between the first and second indentations.

The overhanging portions of the door allow the technician to engage thedoor readily with a finger or tool and to swing the door out of the wayduring installation of a connector in the socket. To further facilitatethis action, it is also preferable that the door has a projectionextending rearwardly on a side of the door remote from the hinges, sothat the technician can engage the projection to open the door.

The housing desirably has at least two resilient panel extensionsprojecting outwardly from the housing in vertical directions, lateraldirections or both vertical and lateral directions beyond the dimensionsof the panel mounting portion. The panel extensions are disposedrearwardly of the panel mounting portion. The panel extensions areinwardly deformable so that the housing can be advanced into a panel andthe panel extensions will deform inwardly to pass through an opening ina panel and return outwardly to hold the socket in the panel. The socketmay further include engagement projections projecting outwardly from thehousing in vertical directions, lateral directions or both vertical andlateral directions beyond the dimensions of the panel mounting portion.The engagement projections are spaced forwardly of the panel extensionsso that a panel can be engaged between the engagement projections andthe panel extensions. The panel extensions work with the engagementprojections to allow the socket housing to be inserted into a hole in apanel and have the housing be secured in the hole. Desirably, each panelextension includes a portion of a lateral wall of the housing. Each suchlateral wall has a U-shaped slot bordering such portion of the wall sothat each such wall portion forms a tongue connected to the remainder ofthe wall only at the at the rearward end of the tongue.

In yet another aspect of the present invention, a fiber optic connectorincludes a housing having forward and rearward directions. The housinghas an interior passage extending forwardly and rearwardly. A pair ofstops is also provided projecting into the passageway. The stops arespaced apart from one another in a first direction transverse to theforward and rearward directions. The housing has interior guide surfacesbounding the passageway to the rear of the stop surfaces and slopingoutwardly away from one another in the rearward direction. A ferrule isfurther provided having a front end and a rearward portion. At least onefiber bore for holding an optical fiber extending into the ferrule fromthe front end, and at least one pin-receiving bore parallel to the fiberbore extending into the ferrule from the front end are provided. Therearward portion of the ferrule has a dimension in the first directiongreater than the dimension of the opening between the stops. The ferruleis slidably disposed in the housing with the rearward portion disposedto the rear of the stops. The ferrule is movable between a forwardposition in which the ferrule is engaged with the stops and a rearwardposition in which the ferrule is disengaged from the stops. Guidesurfaces constraining the ferrule in at least one direction transverseto the forward and rearward directions when the ferrule is in theforward position are also provided. The constraint is released due tothe slope of the guide surfaces as the ferrule moves rearwardly in thehousing. Also provided is a spring biasing the ferrule forwardly againstthe stops. This aspect of the invention provides a unit that tends tokeep the ferrule centered in the connector housing before the connectorsare mated, thus facilitating proper alignment when connectors are mated.Stubbing of the guide pins is thus minimized. However, the ferrule canfloat or move laterally with respect to the housing during mating.

Preferably, the guide surfaces constrain the ferrule in all directionstransverse to the forward and rearward directions when the ferrule is inthe forward position. More preferably, the housing has upward anddownward directions transverse to the axial direction and lateraldirections transverse to the axial direction and transverse to saidupward and downward directions. The passageway desirably is generallyrectangular in cross-section and has vertical walls facing laterallyinwardly toward one another and horizontal walls facing upwardly anddownwardly toward one another. The guide surfaces desirably include afirst pair of guide surfaces extending along the vertical walls and asecond pair of guide surfaces extending along the horizontal walls. Theferrule desirably has a forward portion defining the front end of theferrule and projecting between the stops. More preferably, the stopsdefine rearwardly-facing seating plane surfaces. The ferrule further hasforwardly-facing shoulder surfaces engaged with the seating planesurfaces when the ferrule is in the forward position. Desirably, thesecond pair of guide surfaces include a pair of straight wall regionsextending rearwardly from the seating plane surfaces and a pair ofsloping wall regions extending from said straight wall regions.

The ferrule may be a molded element having a parting line. The partingline extends forwardly and rearwardly in the body. The body has slotsextending forwardly and rearwardly and are aligned with the partingline, whereby the slots provide clearance for the parting line. Thisaspect of the invention incorporates the realization that in the moldingprocess used to form the ferrule, irregularities may be formed along theparting line. The slots allow a clearance around the parting line toaccommodate any such irregularities. This further reduces thepossibility of misalignment of the fiber optics or stubbing of the guidepins.

In another aspect of the present invention, a method of providingmatable fiber optic connectors preferably comprises the following steps:providing a plurality of terminated fiber optic cable ends, each suchcable end having thereon a housing and a ferrule unit resilientlymounted in the housing. Each such ferrule unit has an exposed forwardface and the optical fibers of the cable extend to exposed ends at suchforward face. Each such ferrule unit further having one or morepin-receiving bores extending rearwardly from such forward face inpredetermined locations relative to the exposed ends of the fibers. Eachsuch pin-receiving bore desirably includes a clearance portion adjacentthe forward face of the ferrule unit and an interference-fit portionhaving at least one dimension smaller than the interference-fit portionremote from the forward face. Another step includes selectively makingsome of the cable ends into male ends or hermaphroditic ends by engagingpins in at least some of the pin-receiving bores of the ferrule units onsuch ends so that such pins are forcibly engaged in the interference-fitportions of the pin-receiving bores and such pins project beyond theforward face of the ferrule unit. The pin-engaging step is performedwhile the housings and ferrule units remain in place on the cable ends.

Preferably, the step of making at least some of the cable ends into maleends or hermaphroditic ends includes the step of making such ends maleends by inserting pins into all of the pin-receiving bores of thoseends. Desirably, each pin has a groove at a proximal end. The proximalends of the pins are engaged in the interference-fit portions of thepin-receiving bores. A related aspect of the present invention providesa method of providing matable fiber optic connectors comprising thesteps of providing a plurality of terminated fiber optic cable ends.Each such cable end has thereon a housing and a ferrule unit resilientlymounted in the housing. Each such ferrule unit has an exposed forwardface and has optical fibers of the cable extending to exposed ends atsuch forward face. Each such ferrule unit further has one or morepin-receiving bores extending rearwardly from such forward face inpredetermined locations relative to the exposed ends of the fibers. Eachsuch pin-receiving bore includes a clearance portion adjacent to theforward face of the ferrule unit and an interference-fit portion havingat least one dimension smaller than the interference-fit portion remotefrom the forward face. At least some of the cable ends are male orhermaphroditic cable ends having pins forcibly engaged in theinterference-fit portions of at least some of the pin-receiving boresand projecting beyond the forward faces of the ferrule units. The methodfurther includes converting at least some or the male or hermaphroditicends to female ends by extracting the pins from the ferrule units ofsuch ends while the housings and ferrule units remain in place on thecable ends.

Methods according to these aspects of the invention provide for fieldinsertion or field removal of the pins and hence allow the technician inthe field to mate up any cable end to any device or mating end, withoutregard to whether the cable ends are originally male or female.

Another aspect of the present invention discloses a terminated fiberoptic cable end comprising a fiber optic cable including one or morefibers, a housing mounted on an end of the cable, and a ferrule unitresiliently mounted in the housing. Each such ferrule unit has anexposed forward face and has optical fibers of the cable extending toexposed ends at such forward face. Each such ferrule unit further hasone or more pin-receiving bores extending rearwardly from such forwardface in predetermined locations relative to the exposed ends of thefibers. Each such pin-receiving bore includes a clearance portionadjacent to the forward face of the ferrule unit and an interference-fitportion has at least one dimension smaller than the interference-fitportion remote from the forward face.

Preferably, the terminated fiber optic cable ends further comprise pinsin the pin-receiving bores of the ferrule unit. Each of the pins has aproximal end engaged in the interference-fit portion of one of thepin-receiving bore. Each pin has a distal end projecting through theclearance portion of the pin-receiving bore beyond the forward face ofthe ferrule unit. More preferably, the proximal end of each pin includesa tapered proximal tip, a groove encircling the pin, and a cylindricalportion between the tapered proximal tip and the groove. Each pin alsoincludes a cylindrical main region extending from the groove toward thedistal end of the pin. Preferably, the ferrule unit includes a ferruledefining one or more fiber bores holding said fibers. The ferrule alsodefines the clearance portions of one or more pin-receiving bores. Theferrule unit also includes a pin retainer formed separately from theferrule and defining interference fit portions of one or morepin-receiving bores. Alternatively, the pin retainer may comprise blindholes into which the pins are inserted.

Desirably, the pin-retainer has a slot extending to eachinterference-fit portion so that the interference-fit portion of eachpin-receiving bore can expand to accommodate insertion and removal ofpins. The ferrule unit desirably includes two pin-receiving bores andtwo fiber bores, the pin-receiving bores and fiber bores being disposedin a common plane. The pin retainer desirably has a central opening inthe common plane, where the fibers pass through the central opening.Preferably, the pin retainer has an entry slot extending transverse tothe common plane. The ferrule has a rear face and a central openingextending into the ferrule from the rear face in the common plane. Theferrule also has a front wall defining a front face of the ferrule unit.The fiber bores of the ferrule extend through the front wall to thecentral opening of the ferrule. The cable end desirably furthercomprises a hollow tubular ferrule plug having front and rear ends and acentral passageway extending between such ends. The front end of theferrule plug is disposed in the central opening of the ferrule. The rearend of the ferrule plug is disposed in the central opening of the pinretainer. The ferrule plug maintains the pin retainer in alignment withthe ferrule. Also preferably, the cable is a ribbon cable that includesa pair of buffered fibers side-by-side. The ribbon cable extends intothe central passageway of the ferrule plug. The cable includes a pair offibers each having an outer buffer and an inner buffer. The outerbuffers of the fibers terminate just to the rear of the ferrule plug,with portions of the fibers covered by the inner buffers extending intothe central passageway. The outer buffers of the fibers have diameterslarger than the height of the central passageway in the ferrule plug,whereby upon rearward movement of the ferrule, the ferrule plug willbear on the outer buffers of the fibers to minimize flexing of fibers.

The cable end may further comprise a spring engaged between the housingand the pin retainer biasing the pin retainer forward relative to thehousing to thereby maintain the pin retainer in engagement with theferrule and bias the entire ferrule unit forwardly relative to thehousing. Desirably, the pin retainer has a rear surface and a recess inthe rear surface. The spring may be a coil spring encircling the fibersof the cable and engaged in the recess.

In a related aspect of the present invention, a method of making aterminated fiber optic cable end comprises the following steps.Assembling a ferrule having a rear surface, a central passageway open tothe rear surface, a front wall, one or more fiber bores extendingthrough the front wall to the central opening and pin-receiving boresextending from the front wall to the rear surface, with a ferrule plughaving a central passageway so that the ferrule plug is received in thecentral opening and the ferrule plug projects rearwardly from the rearsurface of the ferrule. Assembling one or more optical fibers of a cablewith the ferrule so that each such fiber extends through the passagewayof the ferrule plug and through one of the fiber bores in the ferrule,and fastening the fibers to the ferrule. Assembling a pin retainer withthe plug and ferrule to form a ferrule unit. The rearwardly-projectingportion of the ferrule plug engaging in a central opening of the pinretainer. The ferrule plug holds the pin retainer in alignment with theferrule so that pin-receiving bores in the pin retainer are aligned withpin-receiving bores in the ferrule.

Preferably, the method further comprises the step of placing the pinretainer on the fibers remote from the ferrule and plug so that thefibers extend through the central opening of the pin retainer. The stepof assembling the pin retainer to the ferrule and plug includes the stepof sliding the pin retainer forwardly along the fibers to the ferruleand plug. More preferably, the step of placing the pin retainer on thefibers includes the step of passing portions of the fibers remote fromthe ends of the fibers through an entry slot in the pin retainer intothe central opening of the pin retainer. Desirably, the method furthercomprises the step of assembling a housing and a spring to the ferruleunit. The method described above allows a technician to insert andwithdraw the guide pins without having to remove or replace the entireconnector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a connector and coupler according to oneembodiment of the present invention.

FIG. 2 is a top plan view of the housing engaged in the socket accordingto one embodiment of the present invention.

FIG. 3 is a top view of the socket and housing of FIG. 2.

FIG. 4 is a side plan view of the socket and housing of FIG. 2.

FIG. 5 is a front plan view of the socket and housing of FIG. 2.

FIG. 6 is a diagrammatic perspective view of a coupler according to oneembodiment of the present invention.

FIG. 7 is a top plan view of the coupler in FIG. 6 where the coupler isengaging the housing of the MT-RJ connector.

FIG. 8 is a top plan view of the coupler of FIG. 6 where the door isclosed.

FIG. 9 is a side elevational view of the coupler of FIG. 6.

FIG. 10 is a front elevational view of the coupler of FIG. 6.

FIG. 11 is a diagrammatic side cross-sectional view of a housing engagedwith the socket according to one embodiment of the invention.

FIG. 12 is a top cross-sectional view of the housing and ferruleaccording to one embodiment of the present invention.

FIG. 13 is a side cross-sectional view of the housing and ferrule ofFIG. 12.

FIG. 14 is a top cross-sectional view of the ferrule according to oneembodiment of the invention.

FIG. 15 is a side cross-sectional view of the ferrule of FIG. 14.

FIG. 16 is a rear view of the ferrule of FIG. 14.

FIG. 17 is a front view of the pin retainer according to one embodimentof the present invention.

FIG. 18 is a top view of the pin retainer of FIG. 17.

FIG. 19 is a side cross-sectional view of the pin retainer of FIG. 17showing a pin engaged in the pin retainer.

FIG. 20 is a top cross-sectional view of a pin retainer according toanother embodiment of the present invention showing a pin engagedtherein.

FIGS. 21A-21F are assembly diagrams showing successive stages of anassembly process according to one embodiment of the present invention,with certain parts depicted as transparent for clarity of illustration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a fiber optic connector 10 along with a coupler 20are shown. The coupler 20, as best seen in FIGS. 2-5 has two hollowsockets 22 a and 22 b with interior bores 23 and 24 in these socketscommunicating with one another. Certain features of the socket, couplerand connector are explained below with reference to directions such as“upwardly,” “forwardly,” “rearwardly” and “laterally.” These directionsare orthogonal to one and other as illustrated in FIG. 1. As shown inFIG. 1, the “forward” direction is the direction in which the connector10 is advanced when the connector is inserted into the socket 22. Thesedirections are given in the frame of reference of the socket, couplerand connector itself, and need not bear any relation to thegravitational frame of reference. Merely by way of example, the couplerdepicted in FIG. 1 could be rotated 90° about its forward-to-rearwardaxis, so that the upward and downward directions of the coupler wouldlie in the horizontal direction of the drawing.

The coupler 20 is formed from a polymer such as polycarbonate and has apanel-engaging center part 17 and two flat mounting lugs 25 extendingfrom the center part 17 in the upward and downward directions. Mountinglugs 25 have mounting slots 26 at their upper and lower ends. Themounting lugs 25 and the mounting slots 26 are used to secure thecoupler 20 to a panel or other body. A screw (not shown) can be set intoeach mounting slot 26 so that the lug 25 lies between the head of thescrew and the surface where the coupler is to be attached.

Bore 23 has a generally rectangular main portion 23 a with a smallerrectangular keyway portion 23 b along the top of the main portion. Thiskeyway only allows one way for the connector 10 to be inserted, asexplained below. Bore 24 has an identical configuration.

This keyway design is also reflected on the exterior of the coupler 20,as best seen in FIGS. 2-5. Thus, the exterior profile of socket 22 aincludes a principal portion 21 a housing the main portion 23 a of thebore, and a top portion 21 b housing keyway portion 23 b. Top portion 21b is narrower than principal portion 21 a, so that the exterior of thehousing provides indentations in the form of elongated ledges 27extending forwardly and rearwardly along the top of socket 22 a. Theseledges provide a visual and tactile reference indicating the orientationof the keyway. These ledges 27 reflect the contours of the keyway; thekeyway portion 23 b is disposed between the ledges or indentations 27.The same arrangement is provided on socket 22 b. The ledges 27 aid thetechnician to quickly and easily identify the correct orientation forthe connector 10 to be inserted into the socket. The bottom surface 8 ofeach socket 22 a and 22 b is recessed upwardly from the bottom of thepanel engaging portion 17.

Each socket 22 also has a latch pocket 28 extending from the top of thesocket and intersecting the keyway portion of its bore 23 or 24. Thefeatures associated with each latch pocket 28 are identical to thecorresponding features of the socket illustrated in FIG. 11, describedbelow.

As shown in FIG. 11, a single-sided socket includes a body 122 defininga rear face 101 and a bore 124 extending in a forward direction (to theleft as seen in FIG. 11) from rear face 101. The socket incorporatesmounting lugs 125 with openings 126 for receiving screws (not shown) orother fasteners for holding the socket in place. When the socket is usedwith a device such as a transceiver 110, the active optical componentsof the transceiver 110 are mounted in precise relationship to theinterior bore of the housing so that they will be aligned with the fiberoptics of the mating connector. The transceiver typically will have pins112 projecting rearwardly into bore 124 for engagement with a femaleferrule on the mating coupler.

Bore 124 has a configuration identical to bores 23 and 24 discussedabove with reference to FIGS. 1-5. Thus, bore 124 includes a mainportion 124 a and a keyway portion 124 b at the top of the main portion,the keyway portion defining a top interior surface 103 of the bore. Thelatch pocket 128 extends downwardly through the top wall of the socketso that pocket 128 is open to the top interior surface 103 of the bore.The latch pocket has a forwardly-facing catch surface 105 intersectingthe top interior surface of the bore. The top interior surface 103 ofthe bore includes a ramp surface 103 a sloping downwardly in the forwarddirection and extending from the rear face 101 to the vicinity of latchpocket 128 and catch surface 105.

A connector 10 according to a further embodiment of the inventioncomprises a housing 12 that has a main portion 11 and a forward portion13 extending from the main portion. The interior of the connector 12further comprises a ferrule 40, a ferrule plug 50, a pin retainer 60, aspring 70, a crimp nut 72, a crimp ring 74, and a boot 76. As shown inFIG. 1, the connector is used with an optical cable including an outerjacket 80 covering a pair of sheathed fibers 82.

The connector housing 12, best seen in FIG. 11, is formed from a polymersuch as polycarbonate housing 12 and has a latch arm 33 that is attachedto the connector housing by a flexible, beam-like latch release memberhaving an upwardly sloping portion 35 extending forwardly from the rearof the housing main portion 11, and having a downward projection 37extending to the junction with the latch release arm. A barb 38 islocated at the distal end of the latch arm 33, remote from projection37.

As best seen in FIGS. 2 and 11, the forward portion 13 of connectorhousing 12 is received into the bore 24 or 124 of the socket, leavingthe main portion 11 exposed. The main portion 11 has an increasedexposed surface area for grasping the connector 10 during withdrawalfrom the socket. Grip like features 31, in the form of ridges andgrooves, on all four sides of the connector housing main portion 11,particularly on top and bottom, enhance the holding and grasping of theconnector during insertion and withdrawal.

The connector housing 12 also has a key portion 39 located on the top ofthe forward portion 13 on the housing. The key portion 39 is arectangular projection from the top of the forward portion thatdetermines the proper orientation for engagement of the connector intothe socket. The forward portion and key portion give the connectorhousing a profile that corresponds to the outline of the socket bore.When the connector housing 12 and coupler 20 are engaged, only theforward portion 13 is received in the bore of the socket. The properorientation is established as the key portion 39 on the forward portionof the housing is engaged in the keyway 24 b (FIG. 4) or 124 b (FIG. 11)of the socket bore. The barb 38 located on the latch arm 33 engages withthe latch pocket 28 or 128 on the socket, thus securing the connectorhousing 12 to the socket 20. A rearwardly-facing surface on barb 38engages with the forwardly-facing catch surface 105 (FIG. 11) on thehousing.

There is a clearance or spacing between arm 33 and ramp surface 103 a atand near the rear face 101 of the socket. This clearance preventsengagement between the open end of the socket and the proximal portionof the latch arm 33, remote from barb 38, if the connector housing 12 isdisplaced upwardly relative to the socket during service. If theclearance were not present, such engagement could cause the latch arm tobend downwardly and could cause accidental disengagement of barb 38 fromthe latch pocket.

The geometry of the latch release member decreases the stiffness at thejunction of the upwardly sloping portion 35 and the downward projection37. In particular, the stiffness in region 36 at the juncture of theseportions should be limited. Surprisingly, it has been found thatreducing the stiffness of the latch release member, particularly atregion 36, actually reduces the tendency of the latch arm 33 to deflectdownwardly in response to rearwardly-directed forces on body 12. This inturn minimizes the tendency of latch arm 33 to bend away and disengagethe barb. Desirably, the latch release member, including portions 35 and37, is less about 1 mm thick or less and hence is relatively flexible.

The size or profile of the main portion 11 of the connector housing ismatched to the size of the socket 22 or 122. The bottom surface 32 ofthe connector housing is substantially coplanar with the bottom surface8 or 108 (FIGS. 4 and 11) of the socket. Alternatively, the bottomsurface of the connector housing may project slightly below the bottomsurface of the socket 20.

Also, the lateral surfaces 31 of the connector housing main portion 11are coplanar with the lateral surfaces 9 of the principal portion of thesocket (FIGS. 2 and 3). Alternatively, surfaces 31 may protrude slightlyin the lateral direction beyond the surfaces 9 of the socket. Thecoplanar or protruding bottom and lateral surfaces of the connector mainportion make it easy for the technician to grasp the main portion 11during insertion or removal of the connector in the socket. The socketdoes not block the technician's fingers from engaging the connectorhousing. Moreover, the substantially coplanar surfaces provide a“streamlined” appearance to the completed assembly.

The coupler 220 illustrated in FIGS. 6-10 is similar to the coupler asdescribed in FIGS. 1-5 in that it has two hollow sockets 222 a and 222 bback to back, with the interior bores 223 and 224 (FIG. 9) of thesesockets communicating with one another. A door 14 is incorporated intothe socket 222 a at one end of the coupler 220 for the purpose ofkeeping particulates from entering the optical interface, and for thepurpose of blocking light emission from an optical system. Thus, if anactive device such as an optical transceiver is connected to coupler 220disposed in the bore 223 without door 14, and no connector 10 isconnected in the bore 224 equipped with door 14, the door will blocklight emitted by the transceiver from passing out into the environment.

The door has an upper hinge 16 a with a pin projecting downwardly and alower hinge 16 b with a pin projecting upwardly in alignment with theupper hinge pin. A spring 15 includes a short, two-turn metal wire coilwith a pair of arms projecting from the coil. The hinges 16 and spring15 are designed in such a way that when assembled to the socket 222 andin closed position, the door with hinge and spring do not extend beyondthe maximum width (w) and height (h) (FIG. 10) of an industry-standardMT-RJ socket. An industry-standard RJ type socket has a height (h) of10±0.1-mm and a width (w) of 9.3±0.1-mm, and the socket according tothis aspect of the invention, including the door 14, desirably has thesame width and height. Therefore, the socket 222 a according to thisaspect of the invention will fit into a panel opening of the sizenormally used to hold an MT-RJ socket, i.e. typically about 10.1-mm highand 9.4-mm wide or larger.

The socket 222 a has a panel-engaging portion 217 remote from the openend of the socket having the maximum width and height. As explained ingreater detail above with reference to FIGS. 1-5, the housing of thesocket 222 a has reduced dimensions in the top portion around theinternal keyway portion of the bore so that the socket defines exteriorindentations in the form of ledges 227 a (FIGS. 6 and 7) and 227 b (FIG.7) in the top of the socket 222 a. The top hinge 16 a of the door 14 andthe spring 15 are accommodated in indentation 227 a. The bottom externalsurface 201 (FIG. 9) of the socket 222 a near the rear face of thesocket (to the right in FIG. 9) is recessed upwardly relative to thebottom surface of the panel-engaging portion 217. The bottom hinge 16 bis accommodated in this recess. The pin of top hinge 16 a is arranged tofit into an upwardly-facing depression 18 a on the upwardly facingsurface of ledge 227 a. The coil of spring 15 surrounds the pin of upperhinge 16 a. The pin of lower hinge 16 b fits into a similar depression18 b (FIG. 9) in bottom surface 201.

The door 14 is designed with two overhang features 19A and 19B, and oneforward extension 21, allowing the door to be grabbed and manipulatedfrom three separate directions or locations when the door is closed.Thus, one overhang feature 19A of the door lies in front of ledge 227 b(FIG. 8) on the top of the socket and on the side of the socket remotefrom hinges 16. The other overhang 19B projects downwardly beyond therecessed bottom surface 201 (FIG. 10). Extension 21 projects forwardlyon the edge of the door 14 remote from hinges 16. These features provideeasy opening of the door. The door, hinges and spring all fit within thevertical and lateral dimensions of panel-engaging portion 217.

The socket has mounting lugs 225 similar to the mounting lugs projectingupwardly and downwardly from panel-engaging portion 217. Two panel stops29 are molded in socket 222 a. Each panel stop 29 is formed as a tongueportion of a lateral wall, each such tongue portion being separated fromthe remainder of the wall by a U-shaped slot 30, as best shown in FIG. 9so that the tongue is attached to the remainder of the wall at the rearend of the tongue. The socket, and hence the entire coupler, can bemounted in a panel opening corresponding to the panel-engaging portion217. The rear or door end of socket 222 a is inserted through the panelopening. Because the entire door assembly is has lateral and verticaldimensions no larger than those of panel-engaging portion 217, the doorpasses through the cutout in the panel. The panel stops 29 depress,allowing the socket 222 a to be inserted into the panel opening, andthen extend to secure the socket in the panel opening without benefit ofscrews or other holding devices. Once the socket has been inserted inthe panel opening, the panel is caught between panel stops 29 andmounting lugs 225. However, screws or other fasteners can be engaged inthe mounting slots 26.

The internal structure of connector 10 is discussed below. Ferrule 40can be formed from a thermosetting polymer or from a thermoplasticliquid crystal polymer. Ferrule 40 has a rectangular body with a forwardportion 302 and larger rectangular head 341 at its rear end (FIGS. 14and 15). Head 341 defines a forwardly-facing shoulder 339 at thejuncture of the head with the forward portion 302. The ferrule also hasa pair of pin-receiving bores 343 extending front to rear. A pair offiber-receiving bores 345 extend rearwardly from the front face 301 ofthe ferrule. Fiber-receiving bores 345 lie in a common horizontal planewith the pin-receiving bores 343. Each of bores 345 includes a narrow,fiber-constraining portion at the juncture of the bore and front face301. These portions have interior diameters closely matched to the outerdiameter of the unbuffered (bare) fiber. Each bore 345 also includes alarger-diameter portion 347 remote from the front face 301. Ferrule 40further includes a central opening 349 extending forwardly into theferrule from the rear end of the ferrule, in alignment with fiber bores345. A top opening 351 communicates with central opening 349 at thejuncture of the central opening 349 and the clearance portions 347 ofthe fiber bores.

Connector housing 12 has an internal passageway 47 (FIGS. 12 and 13)extending forwardly and rearwardly through the housing. The passagewayis generally rectangular in cross-section, and is bounded by laterallyopposite vertical walls 303 (FIG. 12), top wall 307 and bottom wall 309(FIG. 13). A pair of openings 43, one of which is visible in FIG. 1 andFIG. 11, extend through vertical walls 303 of the housing in forwardportion 13 and communicate with passageway 47. A pair of stops 44 (FIG.12) project into passageway within the forward part 13 of the connectorhousing from vertical walls 303 on opposite sides of the passageway.Stops 44 define an opening between them larger than the width of theforward portion 302 of ferrule 40, but smaller than the width of head341. Stops 44 define rearwardly-facing seating plane surfaces (facing tothe right in FIG. 12) in a common plane. Lateral guide surfaces 49extend rearwardly from each stop 44 along vertical walls 303. Eachlateral guide surface includes a straight wall region 49 a adjacent tothe stop 44 and a sloping wall region 49 b to the rear of the straightwall region 49 a. Each sloping wall region 49 b slopes laterallyoutwardly in the rearward direction. The connector housing also hasvertical guide surfaces 42 (FIG. 13) on top wall 307 and bottom wall 309adjacent stops 44. The vertical guide surfaces slope upwardly anddownwardly, away from one another, in the rearward direction. Thestraight wall regions 49 a of the lateral guide surfaces are spacedapart from one another by a distance just slightly larger than the widthof head 341 on the ferrule. The forwardmost parts of the vertical guidesurfaces are spaced apart from one another by a distance just slightlylarger than the vertical dimension of head 341. Thus, when the ferruleis in the forward position depicted in solid lines in FIGS. 12 and 13,with the shoulder 339 of the ferrule abutting stops 44 and with thefront face 301 of the ferrule projecting out of the front end of housing12, the head of the ferrule is closely constrained by the guide surfacesso that the ferrule is centered with respect to the housing. However,when the ferrule is displaced to the rearward position partiallyindicated in broken lines at 341′ in FIGS. 12 and 13, the head of theferrule is remote from guide surfaces 42 and 49, as indicated at 341′.In this condition, the guide surfaces do not constrain the ferruleagainst lateral and vertical movement with respect to housing 12. Inthis condition, the ferrule can “float” or move laterally and verticallywith respect to the housing and can tilt relative to the housing.

The housing further has a pair of slots 306 extending through thevertical walls 303. As best seen in FIG. 13, these slots extendrearwardly from the front of the housing to the guide surfaces 42 and49, and hence extend rearwardly through stops 44. Slots 306 provideclearance around the horizontal mid-plane of the ferrule, and thus canaccommodate defects such as “flash” or unintended projections formed onthe ferrule forward part 302 at the parting line 308 resulting from amolding process used in manufacturing the ferrule.

The connector further includes a pin retainer 60, illustrated in FIGS.14-19. The pin retainer has a central opening 64 of generallyrectangular cross-section and of the same size as the central opening349 in the ferrule. A partially conical recess 62 is provided in therear surface of the pin retainer. An entry slot 63 extends into thecentral opening from the top of the pin retainer. A pair ofpin-receiving bores 53 extend forwardly and rearwardly through the pinretainer on laterally opposite sides of central opening 64. Eachpin-receiving bore 53 has a pair of pin engagement flats 52 adjacent theforward end of the pin retainer. Flats 52 have rearwardly-facing rampsurfaces 54 sloping outwardly at an oblique angle to the forward andrearward directions, and have forwardly facing stop surfaces 58substantially perpendicular to the forward and rearward directions.

Each pin 55 (FIGS. 14 and 19) has a groove 56 adjacent a proximal end ofthe pin and has tapered surfaces 57 at its proximal and distal ends.Apart from the grooves and tapered surfaces, the pins are of uniformdiameter. The pins desirably are formed from a metal such as steel.

Ferrule plug 50 is a generally tubular elastomeric element having arectangular exterior cross-section closely matched to the dimensions ofthe central passage 349 in the ferrule and the central passage 64 in thepin retainer. The ferrule plug has an interior bore 51. The height ofthe interior bore, seen in FIG. 15, desirably is about 0.4 mm. Thelateral width of the interior bore, seen in FIG. 14, desirably is about1.15 mm at the rear end of the ferrule plug and gradually decreases toabout 1 mm at the forward end of the ferrule plug.

Crimp nut 72 is a polymeric element incorporating a housing 364, havinga pair of projections 360 extending forwardly from the housing.Projections 360 have snaps 362 extending laterally outwardly from theprojections. A hollow boss 368 extends rearwardly from housing 364.Crimp ring 74 is a hollow metallic tube. Boot 76 is a tubular elementformed from an elastomeric material. Spring 70 is a cylindrical metalliccoil spring.

An assembly process is shown in sequence in FIGS. 21A-21F. As shown inFIG. 21A, the spring 70, crimp nut 72, crimp ring 74 and boot 76 areplaced onto the cable. The outer jacket of cable 80 is split (FIG. 23B).The forward ends of buffered fibers 82 are pulled out of the outerjacket 80 and stripped as shown to provide portions 81 having 250 microninner buffers exposed, and unbuffered forward ends 87. Ferrule 40 andferrule plug 50 are assembled to the fiber ends. The forward end of theferrule plug is received in the central passage 349 of the ferrule(FIGS. 14 and 15). The forward ends of fiber portions 81 are insertedinto the interior bore 51 of the ferrule plug and guided by the ferruleplug so that the forward ends of these portions enter into the fiberbores 345, leaving unbuffered tips 87 projecting from the forward end ofthe ferrule. The fibers 81 and ferrule plug 50 are cemented in place byapplying an adhesive such as an epoxy through the top opening 351 of theferrule plug. The fiber ends 87 are polished flush with the front face301 of the ferrule, leaving the assembly in the condition shown in FIG.21B. At this stage, the ferrule plug 50 projects rearwardly from theferrule 40.

Next, the pin retainer 60 is placed onto the buffered fibers 82 from theside. During this operation, the fibers pass through the entry slot 63(see FIGS. 16 and 17) of the pin retainer 60, into the central opening64 of the pin retainer, and the pin retainer is slid forwardly along thefibers until it abuts the rear face of the ferrule 40. In thiscondition, the rearwardly projecting portion of the ferrule plug 50 isengaged in the central opening 64 of the pin retainer. At this stage,the ferrule 40 and pin retainer 60 form a ferrule unit. The ferrule plugmaintains vertical and lateral alignment of the ferrule 40 and pinretainer 60, so that pin-receiving bores 53 of the pin retainer are heldin alignment with the pin receiving bores 343 of ferrule 40, as depictedin FIG. 14. The spring 70 is engaged with the ferrule unit, as shown inFIG. 21C, so that the forward end of spring 70 is engaged in the recess62 in the rear surface of pin retainer 60, as also seen in FIG. 14. Thehousing 12 is then assembled to the crimp nut 72 (FIG. 21D). Theprojections 360 of the crimp nut enter into the interior passage 47 ofconnector housing 12, and snaps 362 on the crimp nut engage in holes 43in the vertical walls of the connector housing. The forward part 302 ofthe ferrule passes through passage 47 of the connector housing, but thehead 341 of the ferrule engages stops 44 within the connector housing inthe manner shown in FIG. 12, so that the connector housing forces theferrule unit, including ferrule 40 and pin retainer 60, rearwardly. Thisplaces spring 70 in compression between the rear surface of the pinretainer and the crimp nut, so that spring 70 biases the ferruleforwardly against the stops 44.

Next, the split cable jacket 80 is advanced over the boss 368 on thecrimp nut, and crimp ring 74 is moved forwardly along the cable so thatthe crimp ring surrounds the boss and cable jacket. The crimp ring iscrimped onto the jacket of the cable (FIG. 21E). The boot is advancedinto place over the crimp ring (FIG. 21F). At this stage, a completefemale connector has been provided on the end of the cable.

The pins 55 can be assembled later, either in the field or at thefactory. To form a male end, two pins are added. To make ahermaphroditic end, one pin is added. The alignment pins 55 are insertedthrough the front of the ferrule 40 after the final assembly of theconnector, while the ferrule and pin retainer are in place in thehousing 12. This adds convenience to the assembly process of theconnector, and provides the flexibility of adding pins 55 based ondemand and/or changing field requirements. The pin engagement flats 52of the pin retainer 60 engage with the groove 56 of the pins (FIGS.17-19). The pins pass freely through the pin-receiving bores 343 of theferrule, until the proximal ends of the pins engage flats 52. Theforwardly facing stop surfaces 58 on the pin retainer (FIG. 19) providea stop to limit rearward travel of the pins during insertion. Thesloping ramp surfaces 54 will allow purposeful extraction of the pins 55from the connector if necessary without destruction. Thus, femaleconnectors can be converted to male connectors by inserting pins 55,whereas male connectors can be converted to female by removing pins, allwhile leaving the connectors otherwise intact. However, the pins of themale connectors stay engaged in the retainer through normal connectorusage.

In a further embodiment (FIG. 20),, a pin retainer 460 is formed from apolymeric material such as a polycarbonate having some flexibility. Thepin-receiving bores 453 are formed as cylindrical blind holes extendinginto the pin retainer from its forward face to closed ends 455. Theinterior diameters of the pin-receiving bores 453 are slightly smallerthan the diameters of pins 55, so that the proximal end of each pin canbe press fit into the pin-receiving bores. The closed ends 455 of thepin-receiving bores control the rearward position of the inserted pins.The pins 55 are retained by a combination of the press fit and theflexible material returning to its original shape and bulging into thegrooves 56 on the pins. The other features of the pin retainer areidentical to those discussed above. Here again, the pins can beassembled after the remaining components of the connector have beenassembled, and can be removed by pulling them forwardly withoutdestroying the connector. Pin retainers according to this embodiment areeasier to mold than the pin retainers discussed above, and provide amore positive stop during assembly of the pins to the connector.

Ferrule plug 50 will accommodate both ribbon type and 900 micron buffercable. The ferrule plug 50 serves to stiffen the otherwise exposed 250micron buffered fibers 81 so as to prevent bending of these fibers andlight loss. If the connector 10 is used with 900 micron buffered cable,the 900 micron buffers 82 of the cable abut the rear end of ferrule plug50 or are placed in close proximity to the rear of the ferrule plug. Asdiscussed below, the ferrule must move rearwardly relative to thehousing 12 during operation. When the ferrule 40 moves back, the 900micron buffers 82 are also forced to the rear; the stripped (250 micron)portions 81 do not bend. When the connector is used with two-fiberribbon cable, the ribbon cable can extend into the interior passageway51 of the ferrule plug.

The connectors as discussed above can be used in the same way as otherstandard MT-RJ connectors. For example, male and female connectors canbe engaged with one another by inserting the forward parts of theconnector housings into the bores 23 and 24 of a double-ended coupler 20as discussed with reference to FIGS. 1-10. Prior to insertion into thecoupler, the front face 301 of the ferrule on each connector protrudesfrom the front of the connector housing. When the connectors areinserted into the coupler, the pins of the male connector enter thepin-receiving bores in the ferrule of the female connector, and thefront faces of the two ferrules engage one another. As the connectorsare engaged in the coupler and move toward one another, each ferrulemust move rearwardly within its connector housing against the bias ofthe spring within the connector. Once both connectors have been fullyseated in the coupler, the ferrules and the ends of the fibers are heldin close abutting contact with one another by the springs in theconnectors. The fibers carried in the two ferrules are precisely alignedwith one another by the engagement between the pins and thepin-receiving bores. This precise alignment is provided even ifimperfections in the coupler or the connector housings introduce somemisalignment between the two connector housings. The ability of theferrules to move laterally and vertically relative to the connectorhousings, and to tilt relative to the connector housings, allows thepins to bring the ferrules into alignment provided that the initialmisalignment introduced by the other components is within the designtolerance range. The connectors also can be employed with a single-sidedsocket having pins arranged in the same manner as a male connector, asillustrated in FIG. 11. In this case, all of the misalignment is takenup by the floating action of the ferrule in the female connector.

Numerous variations and combinations of the features discussed above canbe utilized without departing from the present invention. Merely by wayof example, the features described above can be applied to fiber opticconnectors other than MT-RJ connectors. In a further variant, thearrangement of the stops on the interior of the connector housing can bechanged so that the flat surfaces which arrest the head of the ferruleare disposed along the top and bottom walls of the passageway, ratherthan along lateral walls of the passageway.

A coupler can be made with a door as discussed above with reference toFIGS. 6-10 on both ends. Also, the panel stops can be provided on bothsockets of a double-ended coupler. Doors and other features discussedabove with reference to a socket in a double-ended coupler can beprovided a single-ended socket, and vice-versa. In a further variation,the indentation on the outside of the socket used to accommodate theupper door hinge may be small indentations at the rear end of thesocket; they need not be elongated ledges as illustrated. This variantis less preferred, because it sacrifices the advantages of the elongatedledges in identifying the orientation of the socket. Likewise, therecessed bottom surface which serves to provide clearance for the lowerdoor hinge could be provided only near the rear end of the socket. In afurther variant, the door can be arranged to open upwardly ordownwardly; the hinges and spring can be received in indentations onlaterally-opposite sides of the socket, so that the pivot axis of thedoor is horizontal rather than vertical. The hinges need not includepins received in recesses in the housing. For example, the door or thehousing can be provided with small flexible regions, commonly referredto as “living hinges.” Also, the spring need not be a separate element,but can be incorporated into one of the molded parts. In aless-preferred variant, the spring is entirely omitted and the door mustbe closed manually.

While many of the claims recite complete combinations, it should also beunderstood that further aspects of the present invention includesubcombinations and individual elements included in the foregoingstructures and/or in the combinations recited by the claims.

As these and other variations and combinations can be used, theforegoing description of the preferred embodiments should be taken byway of illustration rather than by way of limitation of the claimedinvention.

What is claimed is:
 1. A socket for receiving a fiber optic connectorhousing, said socket having forward and rearward directions, upward anddownward directions transverse to the forward and rearward directionsand lateral directions transverse to the other said directions, saidsocket defining a bore having an opening at the rearward end of thehousing and extending forwardly into the housing, said housing having apanel mounting portion spaced forwardly from the rear end of thehousing; a door; one or more hinges supporting said door on said housingfor pivoting movement about an axis between a closed position in whichsaid door blocks the opening of the bore and an open position in whichsaid door does not block the opening, and a spring disposed outside ofsaid housing, said door, said hinges and said spring having width andheight dimensions equal to or smaller than the width and heightdimensions of said panel mounting portion.
 2. A socket as claimed inclaim 1 wherein said axis is vertical and wherein housing defines afirst indentation at the rearward end of the housing, and wherein saidhinges include a top hinge disposed in said first indentation.
 3. Asocket as claimed in claim 2 wherein said housing defines a bottomsurface at the rearward end of the housing, said bottom surface beingrecessed upwardly relative to the bottom surface of said panel engagingportion, and said hinges include a bottom hinge overlying said recessedbottom surface.
 4. A socket as claimed in claim 3 wherein said doordefines a bottom overhang which projects downwardly beyond said recessedbottom surface.
 5. A socket as claimed in claim 2 wherein said firstindentation is disposed on one lateral side of the housing and saidhousing defines a second indentation on the opposite lateral side, saiddoor having an overhang portion which is aligned with said secondindentation.
 6. A socket as claimed in claim 5 wherein said housingdefines a main bore and a keyway having width smaller than said mainbore, said keyway being disposed between said indentations.
 7. A socketas claimed in claim 1 wherein said door has a projection extendingrearwardly on a side of said door remote from said hinges.
 8. A socketas claimed in claim 1 wherein said housing has at least two resilientpanel stops projecting outwardly from the housing in verticaldirections, lateral directions or both vertical and lateral directionsbeyond the dimensions of said panel mounting portion, said panel stopsbeing disposed rearwardly of said panel mounting portion, said panelstops inwardly deformable so that the housing can be advanced into apanel and said panel stops will deform inwardly to pass through anopening in a panel and return outwardly to hold the socket in the panel.9. A socket as claimed in claim 8 further comprising mounting lugsprojecting outwardly from the housing in vertical directions, lateraldirections or both vertical and lateral directions beyond the dimensionsof said panel mounting portion, said engagement projections being spacedforwardly of said panel stops so that a panel can be engaged betweensaid engagement projections and said mounting lugs.
 10. A socket asclaimed in claim 8 wherein each said panel stop includes a portion of alateral wall of the housing, each such lateral wall having a U-shapedslot bordering such portion of the wall so that each such wall portionforms a tongue connected to the remainder of the wall only at therearward end of the tongue.